On Fri, 15 May 2020 12:10:08 +0800 Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
> If there are two threads hitting page fault at the same page,
> one thread updates PTE entry and local TLB, the other can
> update local tlb also, rather than give up and do page fault
> again.
>
> ...
>
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1770,8 +1770,8 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
> }
> entry = pte_mkyoung(*pte);
> entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> - if (ptep_set_access_flags(vma, addr, pte, entry, 1))
> - update_mmu_cache(vma, addr, pte);
> + ptep_set_access_flags(vma, addr, pte, entry, 1);
> + update_mmu_cache(vma, addr, pte);
Presumably these changes mean that other architectures will run
update_mmu_cache() more frequently than they used to. How much more
frequently, and what will be the impact of this change? (Please fully
explain all this in the changelog).
> }
> goto out_unlock;
> }
>
> ...
>
> @@ -2463,7 +2462,8 @@ static inline bool cow_user_page(struct page *dst, struct page *src,
> vmf->pte = pte_offset_map_lock(mm, vmf->pmd, addr, &vmf->ptl);
> locked = true;
> if (!likely(pte_same(*vmf->pte, vmf->orig_pte))) {
> - /* The PTE changed under us. Retry page fault. */
> + /* The PTE changed under us, update local tlb */
> + pdate_mmu_cache(vma, addr, vmf->pte);
Missing a 'u' there. Which tells me this patch isn't the one which you
tested!
> ret = false;
> goto pte_unlock;
> }
>
> ...
>
